To moot is to argue, but then your next statement seems to suggest you want the policy to be rolled out across the UK? Are you for or against rolling this policy out across the UK?
I currently live in New Zealand where alcohol is relatively expensive and it has a massive drinking problem for young persons. When I go back to the UK, the problem is about the same, but the young people aren't going broke buying alcohol. I don't think it works. Increasing the price of Tobacco didn't do much to stop smoking, but vaping and preventing smoking in public areas did. Changing social attitudes to smoking is fundamentally what reduced it.
Personally, I think it's better to use the carrot and not the stick. It shouldn't be the responsibility of the state to raise people's children correctly.
I think this works in my experience. As a child, my parents would let me have a small drink with a meal. As I grew up I never felt the need to drink to excess, I knew how alcohol worked. My sibling had the same experience and doesn't drink. My younger sibling still, was prevented from drinking anything and then went crazy when they legally could.